Self-adhesive sheet metal protective film and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, and provides a self-adhesive metal plate protective film and a preparation method thereof. The self-adhesive metal plate protective film comprises a base material layer with the thickness of 0.06 to 0.08 mm and an adhesive layer with the thickness of 0.14 to 0.16 mm, the adhesive layer is prepared from the following raw materials in parts by weight: 30 to 40 parts of ethylene-vinyl acetate copolymer, 25 to 30 parts of organic silicon modified acrylic resin, 15 to 20 parts of maleic anhydride grafted polypropylene, 6 to 8 parts of polytetrafluoroethylene micro powder, 4 to 6 parts of carbon nano tube / SiO2 nano composite material, 3 to 4 parts of nano zinc oxide, 0.8 to 1 part of silane coupling agent and 1.6 to 2 parts of hindered amine light stabilizer. 0.8 to 1.2 parts of an ultraviolet light absorber and 0.4 to 0.6 part of an antioxidant. According to the protective film prepared in the invention, the high-temperature and high-humidity resistance and the aging resistance of the self-adhesive metal plate protective film are improved, and the amount of residual glue is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and specifically, to a self-adhesive metal sheet protective film and a preparation method thereof. Background Art

[0002] In industries such as construction, household appliances, and automobiles, metal sheets such as galvanized steel sheets and aluminum plastic plates are widely used. To protect these metal sheets from corrosion, pollution, scratches and other adverse effects, a protective film is usually coated on their surfaces. However, the self-adhesive metal sheet protective films on the existing market generally face technical problems such as residual glue, poor heat resistance and easy aging.

[0003] Residual glue is a common problem in the application of self-adhesive protective films. When the protective film is torn off, it often leaves difficult-to-remove glue marks on the surface of the protected metal sheet. This not only affects the beauty of the product, but may also cause pollution or damage to the protected surface. The generation of residual glue is often related to the ratio of the protective film glue, the adhesion between the substrate and the glue, and the material of the protected surface. If the glue ratio is improper, or the adhesion between the substrate and the glue is insufficient, or the compatibility with the protected surface is poor, it may lead to glue residue when the film is torn off.

[0004] The self-adhesive metal sheet protective film needs to maintain the stability of its performance in different temperature environments. However, the existing protective films often have problems of poor heat and humidity resistance. In a high-temperature environment, the protective film may soften, deform or even melt, thus losing its protective effect. In a high-humidity environment, the adhesiveness of the protective film may decrease, resulting in poor adhesion or easy detachment. This problem of poor heat and humidity resistance limits the application of the protective film in different temperature environments.

[0005] The self-adhesive metal sheet protective film also needs to withstand the action of various environmental factors during use, such as ultraviolet rays, oxygen, moisture, etc. These factors will cause the aging of the protective film, thus reducing its performance and service life. The aged protective film may have problems such as reduced adhesiveness, embrittlement, discoloration, etc., making it unable to effectively protect the metal sheet.

[0006] To solve the above technical problems, the present invention proposes a new self-adhesive metal sheet protective film and a preparation method thereof. This protective film has excellent anti-residual glue performance, heat resistance and anti-aging performance, and can be widely used for the protection of various metal sheets. Summary of the Invention

[0007] The present invention proposes a self-adhesive metal sheet protective film and a preparation method thereof, which improve the high-temperature and high-humidity resistance and anti-aging property of the self-adhesive metal sheet protective film, and reduce the amount of residual glue.

[0008] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a self-adhesive metal sheet protective film, comprising a substrate layer with a thickness of 0.06 - 0.08 mm and an adhesive layer with a thickness of 0.14 - 0.16 mm; The substrate layer is composed of the following raw materials in parts by weight: 60 - 80 parts of polypropylene, 12 - 14 parts of ethylene-octene copolymer, 4 - 6 parts of nano-silica, 0.3 - 0.5 parts of silane coupling agent, 0.8 - 1 part of hindered amine light stabilizer, 0.5 - 0.7 parts of ultraviolet absorber, and 0.3 - 0.5 parts of antioxidant; The adhesive layer is composed of the following raw materials in parts by weight: 30 - 40 parts of ethylene-vinyl acetate copolymer, 25 - 30 parts of organosilicon-modified acrylic resin, 15 - 20 parts of maleic anhydride grafted polypropylene, 6 - 8 parts of polytetrafluoroethylene micropowder, 4 - 6 parts of carbon nanotube / SiO2 nanocomposite, 3 - 4 parts of nano-zinc oxide, 0.8 - 1 part of silane coupling agent, 1.6 - 2 parts of hindered amine light stabilizer, 0.8 - 1.2 parts of ultraviolet absorber, and 0.4 - 0.6 parts of antioxidant.

[0009] As a further technical solution, the preparation method of the carbon nanotube / SiO2 nanocomposite includes: mixing the pretreated carbon nanotubes with the transparent sol prepared by mixing tetraethyl orthosilicate, ethanol, and water, ultrasonic dispersing for 30 min, stirring at 50 - 60 °C and 100 - 200 rpm for 5 - 6 h, cooling to room temperature and standing for 10 - 12 h, then vacuum drying at 70 - 80 °C for 2 - 3 h to remove the residual solvent, and finally calcining the vacuum-dried material at 380 - 420 °C under nitrogen protection for 2 - 3 h, and naturally cooling to obtain the carbon nanotube / SiO2 nanocomposite.

[0010] As a further technical solution, the pretreatment method includes: placing the carbon nanotubes in an ethanol solution containing 1% surfactant CTAB by mass fraction, ultrasonic treating for 1 - 2 hours to break the agglomeration, centrifuging at 8000 rpm to remove the undispersed particles, and collecting the upper uniformly dispersed liquid; then oxidizing with 20% - 30% nitric acid by mass concentration at 50 - 60 °C for 30 - 40 minutes, washing with deionized water until neutral, and vacuum drying to obtain the pretreated carbon nanotubes.

[0011] As a further technical solution, the preparation method of the transparent sol includes: mixing tetraethyl orthosilicate, ethanol, and water in a molar ratio of 1:4:4, adjusting the pH to 2 - 3 with hydrochloric acid, adding polyvinyl alcohol, and magnetically stirring at 200 - 300 rpm for 2 - 3 hours to form a transparent sol.

[0012] As a further technical solution, the mass of the polyvinyl alcohol is 0.4% - 0.6% of the total mass of tetraethyl orthosilicate, ethanol, and water.

[0013] As a further technical solution, the mass of the pretreated carbon nanotubes is 6%-10% of the mass of the transparent sol.

[0014] As a further technical solution, the silane coupling agent is silane coupling agent KH550.

[0015] As a further technical solution, the hindered amine light stabilizer is hindered amine light stabilizer HALS-622, the ultraviolet absorber is UV-326 ultraviolet absorber, and the antioxidant is antioxidant 168.

[0016] In a second aspect, the present invention provides a method for preparing a self-adhesive metal sheet protective film. The steps include: first, weighing the raw materials of the substrate layer according to a ratio, mixing them, melting and extruding at 160-180°C, filtering, and blowing a film to obtain the substrate layer. Then, corona treating the substrate layer under the conditions of a power of 6-10 kW and a treatment speed of 15-25 m / min. Subsequently, weighing the raw materials of the adhesive layer according to the formula ratio, putting each component into a high-speed mixer and mixing and stirring evenly, and using the gravure coating method to coat on the surface of the substrate layer, and curing to form the adhesive layer to obtain the self-adhesive metal sheet protective film.

[0017] As a further technical solution, the curing step includes: drying under hot air conditions at 80-100°C for 4-6 minutes.

[0018] The working principle and beneficial effects of the present invention are as follows: In the substrate layer of the present invention, both polypropylene and ethylene-octene copolymer have certain high-temperature resistance, and can maintain the structural stability at a relatively high temperature, thereby enhancing the high-temperature resistance of the protective film; nano-silica, as an inorganic nano-particle, can improve the thermal stability and mechanical strength of the material, and helps the protective film to maintain its performance at high temperatures; in the adhesive layer, ethylene-vinyl acetate copolymer has good heat-sealing and heat-bonding properties, and can maintain stable adhesiveness within a certain temperature range, which helps the protective film to maintain its adhesiveness in high-temperature and high-humidity environments; the introduction of organosilicon-modified acrylic resin can improve the temperature resistance and moisture resistance of the resin, so that the adhesive layer can still maintain stable performance in harsh environments.

[0019] In the present invention, the hindered amine light stabilizer can effectively absorb the ultraviolet energy and convert it into harmless heat energy, thereby protecting the material from ultraviolet damage. The UV-326 ultraviolet absorber and HALS act synergistically to further enhance the anti-ultraviolet aging ability of the protective film.

[0020] In the present invention, the carbon nanotube / SiO2 nanocomposite can enhance the structural stability and improve the moisture resistance. The carbon nanotube has excellent mechanical properties and thermal stability, while SiO2, as an inorganic oxide, can enhance the overall structural stability of the material. When they are compounded at the nanoscale, a more compact and uniform structure can be formed, thereby enhancing the high-temperature resistance of the protective film. Moreover, after the two are compounded, they have better chemical stability and moisture resistance compared to when carbon nanotubes and silica are added separately as raw materials, and can effectively block the penetration of water molecules, thus protecting the internal adhesive layer from the influence of moisture and improving the high-moisture resistance of the protective film. In terms of anti-aging performance, the SiO2 layer can block part of the ultraviolet rays and reduce the damage of ultraviolet rays to the inside of the protective film. At the same time, due to its special tubular structure, the carbon nanotube can also play a certain role in scattering and absorbing ultraviolet rays.

[0021] In addition, the nano-zinc oxide in the present invention has strong antioxidant properties and can protect the material from damage by oxidative decomposition. In a high-temperature and high-humidity environment, zinc oxide can absorb and neutralize free radicals, thereby slowing down the aging process of the material. Moreover, nano-zinc oxide itself has high thermal stability, which can further improve the high-temperature resistance of the protective film. Nano-zinc oxide can also strongly absorb ultraviolet rays and convert them into harmless heat energy or scatter them, thereby further reducing the damage of ultraviolet rays to the protective film. Nano-zinc oxide also has certain antibacterial and antifungal properties, which can reduce the erosion of microorganisms on the protective film and keep it clean and hygienic.

[0022] The introduction of the carbon nanotube / SiO2 nanocomposite in the present invention can improve the microstructure and properties of the adhesive layer, making it more uniform and compact. This helps to reduce the amount of residual glue when the protective film is torn off. In addition, the compounding of carbon nanotubes and SiO2 can enhance the adhesion between the adhesive layer and the metal sheet to be protected, making the protective film adhere more firmly to the metal sheet. When torn off, due to the stronger adhesion, the amount of residual glue will also be reduced accordingly. And nano-zinc oxide, as an accelerator, accelerates the curing reaction of the adhesive layer, which is more conducive to forming a more stable and uniform adhesive layer structure, thereby reducing the amount of residual glue. Moreover, the introduction of nano-zinc oxide may also improve the surface properties of the protective film, making it smoother and flatter. This also helps to reduce the friction and adhesion force with the surface of the metal sheet when the protective film is torn off, thereby reducing the amount of residual glue.

[0023] In this case, when nano-zinc oxide is combined with the carbon nanotube / SiO2 nanocomposite, it also has a synergistic effect, jointly improving the high-temperature and high-moisture resistance, anti-aging performance of the self-adhesive metal sheet protective film, and reducing the amount of residual glue. Detailed implementation mode

[0024] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0025] It should be noted that in the present invention, the polypropylene model is PPH-T03; the ethylene-octene copolymer model is DowEngage 8842; the ethylene-vinyl acetate copolymer model is Elvax 460; the model of the silicone-modified acrylic resin is WH-103C, the maleic anhydride grafted polypropylene model is Polybond 3200; the polytetrafluoroethylene micropowder model is ZonylMP1100; the carbon nanotube model is CNT100.

[0026] Example 1 This example provides a self-adhesive metal sheet protective film, including a substrate layer with a thickness of 0.07 mm and an adhesive layer with a thickness of 0.15 mm; The substrate layer is composed of the following raw materials in parts by weight: 70 parts of polypropylene, 13 parts of ethylene-octene copolymer, 5 parts of nano-silica, 0.4 part of silane coupling agent, 0.9 part of hindered amine light stabilizer, 0.6 part of ultraviolet absorber, and 0.4 part of antioxidant; The adhesive layer is composed of the following raw materials in parts by weight: 35 parts of ethylene-vinyl acetate copolymer, 27 parts of silicone-modified acrylic resin, 17 parts of maleic anhydride grafted polypropylene, 7 parts of polytetrafluoroethylene micropowder, 5 parts of carbon nanotube / SiO2 nanocomposite, 3.5 parts of nano-zinc oxide, 0.9 part of silane coupling agent KH550, 1.8 parts of hindered amine light stabilizer HALS-622, 1 part of ultraviolet absorber UV-326, and 0.5 part of antioxidant 168.

[0027] Among them, the preparation method of the carbon nanotube / SiO2 nanocomposite includes: Place the carbon nanotubes in an ethanol solution containing 1% surfactant CTAB by mass fraction, ultrasonically treat for 1.5 hours to break up the agglomerates, centrifuge at 8000 rpm to remove the undispersed particles, and collect the upper layer of the uniformly dispersed solution; then use 25% nitric acid by mass concentration to oxidize at 55 °C for 35 minutes, wash with deionized water until neutral, and vacuum dry to obtain the pretreated carbon nanotubes; Mix tetraethyl orthosilicate, ethanol, and water in a molar ratio of 1:4:4, adjust the pH to 2.5 with hydrochloric acid, add polyvinyl alcohol and carry out magnetic stirring at 250 rpm for 2.5 hours to form a transparent sol; the mass of polyvinyl alcohol is 0.5% of the total mass of tetraethyl orthosilicate, ethanol, and water; The pretreated carbon nanotubes were mixed with the transparent sol prepared from tetraethyl orthosilicate, ethanol and water. After ultrasonic dispersion for 30 min, the mixture was stirred at 55 °C and 150 rpm for 5.5 h. After cooling to room temperature, it was left standing for 11 h. Subsequently, it was vacuum dried at 75 °C for 2.5 h to remove the residual solvent. Finally, the vacuum-dried material was calcined at 400 °C under nitrogen protection for 2.5 h, and after natural cooling, a carbon nanotube / SiO2 nanocomposite was obtained; the mass of the pretreated carbon nanotubes was 8% of the mass of the transparent sol.

[0028] The preparation method of this self-adhesive metal sheet protective film includes the following steps: First, the raw materials of the substrate layer are weighed according to the ratio and then mixed, melted and extruded at 170 °C, filtered, and blown into a film to obtain the substrate layer. The substrate layer is corona treated under the conditions of a power of 8 kW and a processing speed of 20 m / min. Subsequently, the raw materials of the adhesive layer are weighed according to the formula ratio, and each component is put into a high-speed mixer and mixed and stirred evenly. The concave coating method is used to coat the surface of the substrate layer, and it is dried at 90 °C under hot air conditions for 5 minutes to cure and form the adhesive layer, thus obtaining the self-adhesive metal sheet protective film.

[0029] Example 2 This example provides a self-adhesive metal sheet protective film, which includes a substrate layer with a thickness of 0.06 mm and an adhesive layer with a thickness of 0.16 mm; The substrate layer is composed of the following raw materials in parts by weight: 60 parts of polypropylene, 14 parts of ethylene-octene copolymer, 4 parts of nano-silica, 0.5 part of silane coupling agent, 0.8 part of hindered amine light stabilizer, 0.7 part of ultraviolet absorber, and 0.3 part of antioxidant; The adhesive layer is composed of the following raw materials in parts by weight: 40 parts of ethylene-vinyl acetate copolymer, 25 parts of organosilicon-modified acrylic resin, 20 parts of maleic anhydride-grafted polypropylene, 6 parts of polytetrafluoroethylene micropowder, 6 parts of carbon nanotube / SiO2 nanocomposite, 3 parts of nano-zinc oxide, 1 part of silane coupling agent KH550, 1.6 parts of hindered amine light stabilizer HALS-622, 1.2 parts of ultraviolet absorber UV-326, and 0.4 part of antioxidant 168.

[0030] Among them, the preparation method of the carbon nanotube / SiO2 nanocomposite includes: The carbon nanotubes were placed in an ethanol solution containing 1% (mass fraction) of surfactant CTAB, ultrasonically treated for 2 hours to break the agglomeration, and centrifuged at 8000 rpm to remove the undispersed particles, and the upper layer of the uniformly dispersed liquid was collected; subsequently, it was oxidized with 20% nitric acid by mass concentration at 60 °C for 30 minutes, washed with deionized water until neutral, and vacuum dried to obtain the pretreated carbon nanotubes; Mix tetraethyl orthosilicate, ethanol and water in a molar ratio of 1:4:4, adjust the pH to 3 with hydrochloric acid, add polyvinyl alcohol, and then carry out magnetic stirring at 200 rpm for 3 hours to form a transparent sol; the mass of polyvinyl alcohol is 0.4% of the total mass of tetraethyl orthosilicate, ethanol and water. Mix the pretreated carbon nanotubes with the transparent sol prepared from tetraethyl orthosilicate, ethanol and water, ultrasonically disperse for 30 min, then stir at 60 °C and 100 rpm for 6 h, cool to room temperature and let stand for 10 h, then vacuum dry at 80 °C for 2 h to remove the residual solvent, and finally calcine the vacuum-dried material at 420 °C under nitrogen protection for 2 h, and naturally cool to obtain the carbon nanotube / SiO2 nanocomposite; the mass of the pretreated carbon nanotubes is 10% of the mass of the transparent sol.

[0031] The preparation method of this self-adhesive metal sheet protective film includes the following steps: First, weigh the raw materials of the substrate layer according to the ratio, mix them, melt and extrude at 160 °C, filter, and blow film to obtain the substrate layer. Carry out corona treatment on the substrate layer under the conditions of a power of 10 kW and a processing speed of 15 m / min. Then weigh the raw materials of the adhesive layer according to the formula ratio, put each component into a high-speed mixer and mix and stir evenly, coat on the surface of the substrate layer by the gravure coating method, and dry at 100 °C under hot air conditions for 4 minutes to cure and form the adhesive layer to obtain the self-adhesive metal sheet protective film.

[0032] Example 3 This example provides a self-adhesive metal sheet protective film, which includes a substrate layer with a thickness of 0.08 mm and an adhesive layer with a thickness of 0.14 mm. The substrate layer is composed of the following raw materials in parts by weight: 80 parts of polypropylene, 12 parts of ethylene-octene copolymer, 6 parts of nano-silica, 0.3 part of silane coupling agent, 1 part of hindered amine light stabilizer, 0.5 part of ultraviolet absorber, and 0.5 part of antioxidant. The adhesive layer is composed of the following raw materials in parts by weight: 30 parts of ethylene-vinyl acetate copolymer, 30 parts of organosilicon-modified acrylic resin, 15 parts of maleic anhydride-grafted polypropylene, 8 parts of polytetrafluoroethylene micropowder, 4 parts of carbon nanotube / SiO2 nanocomposite, 4 parts of nano-zinc oxide, 0.8 part of silane coupling agent KH550, 2 parts of hindered amine light stabilizer HALS-622, 0.8 part of ultraviolet absorber UV-326, and 0.6 part of antioxidant 168.

[0033] Among them, the preparation method of the carbon nanotube / SiO2 nanocomposite includes: The carbon nanotubes were placed in an ethanol solution containing 1% surfactant CTAB by mass fraction, ultrasonically treated for 1 hour to break up the agglomerates, centrifuged at 8000 rpm to remove undispersed particles, and the upper layer of the uniformly dispersed solution was collected; subsequently, it was oxidized with 30% nitric acid by mass concentration at 50 °C for 40 minutes, washed with deionized water until neutral, and vacuum dried to obtain the pretreated carbon nanotubes; Tetraethyl orthosilicate, ethanol, and water were mixed in a molar ratio of 1:4:4, the pH was adjusted to 2 with hydrochloric acid, polyvinyl alcohol was added, and magnetic stirring was carried out at 300 rpm for 2 hours to form a transparent sol; the mass of polyvinyl alcohol was 0.6% of the total mass of tetraethyl orthosilicate, ethanol, and water; The pretreated carbon nanotubes were mixed with the transparent sol prepared from tetraethyl orthosilicate, ethanol, and water, ultrasonically dispersed for 30 min, stirred at 50 °C and 200 rpm for 5 h, cooled to room temperature and left standing for 12 h, then vacuum dried at 70 °C for 3 h to remove residual solvents, and finally the vacuum-dried material was calcined at 380 °C under nitrogen protection for 3 h, and after natural cooling, a carbon nanotube / SiO2 nanocomposite was obtained; the mass of the pretreated carbon nanotubes was 6% of the mass of the transparent sol.

[0034] The preparation method of this self-adhesive metal sheet protective film includes the following steps: First, the raw materials of the substrate layer are weighed according to the ratio and mixed, melt-extruded at 180 °C, filtered, and blown into a film to obtain the substrate layer. The substrate layer is corona-treated under the conditions of a power of 6 kW and a processing speed of 25 m / min. Subsequently, the raw materials of the adhesive layer are weighed according to the formula ratio, and each component is put into a high-speed mixer and mixed and stirred evenly. The concave coating method is used to coat the surface of the substrate layer, and it is dried at 80 °C under hot air conditions for 6 minutes to cure and form the adhesive layer, thus obtaining the self-adhesive metal sheet protective film.

[0035] Comparative Example 1 This comparative example provides a self-adhesive metal sheet protective film, which includes a substrate layer with a thickness of 0.07 mm and an adhesive layer with a thickness of 0.15 mm; The substrate layer is composed of the following raw materials in parts by weight: 70 parts of polypropylene, 13 parts of ethylene-octene copolymer, 5 parts of nano-silica, 0.4 part of silane coupling agent, 0.9 part of hindered amine light stabilizer, 0.6 part of ultraviolet absorber, and 0.4 part of antioxidant; The adhesive layer is composed of the following raw materials in parts by weight: 35 parts of ethylene-vinyl acetate copolymer, 27 parts of organosilicon-modified acrylic resin, 17 parts of maleic anhydride-grafted polypropylene, 7 parts of polytetrafluoroethylene micropowder, 5 parts of carbon nanotube / SiO2 nanocomposite, 3.5 parts of nano zinc oxide, 0.9 part of silane coupling agent KH550, 1.8 parts of hindered amine light stabilizer HALS-622, 1 part of ultraviolet absorber UV-326, and 0.5 part of antioxidant 168.

[0036] Among them, the preparation method of the carbon nanotube / SiO2 nanocomposite includes: Mix tetraethyl orthosilicate, ethanol and water in a molar ratio of 1:4:4, adjust the pH to 2.5 with hydrochloric acid, add polyvinyl alcohol and then carry out magnetic stirring at a speed of 250 rpm for 2.5 hours to form a transparent sol; the mass of polyvinyl alcohol is 0.5% of the total mass of tetraethyl orthosilicate, ethanol and water; Mix the carbon nanotubes with the transparent sol prepared from tetraethyl orthosilicate, ethanol and water, perform ultrasonic dispersion for 30 min, then stir at 55 °C and 150 rpm for 5.5 h, cool to room temperature and let stand for 11 h, then vacuum dry at 75 °C for 2.5 h to remove the residual solvent, and finally calcine the vacuum-dried material at 400 °C under nitrogen protection for 2.5 h, and naturally cool to obtain the carbon nanotube / SiO2 nanocomposite; the mass of the carbon nanotubes is 8% of the mass of the transparent sol.

[0037] The preparation method of this self-adhesive metal sheet protective film includes the following steps: First, weigh the raw materials of the substrate layer according to the ratio, mix them, melt and extrude at 170 °C, filter, and blow film to obtain the substrate layer. Carry out corona treatment on the substrate layer under the conditions of a power of 8 kW and a processing speed of 20 m / min. Then, weigh the raw materials of the adhesive layer according to the formula ratio, put each component into a high-speed mixer and mix and stir evenly, coat on the surface of the substrate layer by the gravure coating method, and dry and cure at 90 °C hot air for 5 minutes to form the adhesive layer, thus obtaining the self-adhesive metal sheet protective film.

[0038] Comparative Example 2 This comparative example provides a self-adhesive metal sheet protective film, including a substrate layer with a thickness of 0.07 mm and an adhesive layer with a thickness of 0.15 mm; The substrate layer is composed of the following raw materials in parts by weight: 70 parts of polypropylene, 13 parts of ethylene-octene copolymer, 5 parts of nano silicon dioxide, 0.4 part of silane coupling agent, 0.9 part of hindered amine light stabilizer, 0.6 part of ultraviolet absorber, and 0.4 part of antioxidant; The adhesive layer is composed of the following raw materials in parts by weight: 35 parts of ethylene-vinyl acetate copolymer, 27 parts of organosilicon-modified acrylic resin, 17 parts of maleic anhydride grafted polypropylene, 7 parts of polytetrafluoroethylene micropowder, 1.5 parts of carbon nanotubes, 3.5 parts of nano-SiO2, 3.5 parts of nano-zinc oxide, 0.9 part of silane coupling agent KH550, 1.8 parts of hindered amine light stabilizer HALS-622, 1 part of ultraviolet absorber UV-326, and 0.5 part of antioxidant 168.

[0039] The preparation method of this self-adhesive metal sheet protective film includes the following steps: First, weigh the raw materials of the substrate layer according to the proportion, mix them, melt and extrude at 170 °C, filter, and blow film to obtain the substrate layer. Corona treat the substrate layer under the conditions of a power of 8 kW and a treatment speed of 20 m / min. Subsequently, weigh the raw materials of the adhesive layer according to the formula ratio, put each component into a high-speed mixer and mix and stir evenly. Coating is carried out on the surface of the substrate layer by the gravure coating method, and dried for 5 minutes under the condition of 90 °C hot air to cure and form the adhesive layer, thus obtaining the self-adhesive metal sheet protective film.

[0040] Comparative Example 3 This comparative example provides a self-adhesive metal sheet protective film, including a substrate layer with a thickness of 0.07 mm and an adhesive layer with a thickness of 0.15 mm; The substrate layer is composed of the following raw materials in parts by weight: 70 parts of polypropylene, 13 parts of ethylene-octene copolymer, 5 parts of nano-silica, 0.4 part of silane coupling agent, 0.9 part of hindered amine light stabilizer, 0.6 part of ultraviolet absorber, and 0.4 part of antioxidant; The adhesive layer is composed of the following raw materials in parts by weight: 35 parts of ethylene-vinyl acetate copolymer, 27 parts of organosilicon-modified acrylic resin, 17 parts of maleic anhydride grafted polypropylene, 7 parts of polytetrafluoroethylene micropowder, 5 parts of nano-SiO2, 3.5 parts of nano-zinc oxide, 0.9 part of silane coupling agent KH550, 1.8 parts of hindered amine light stabilizer HALS-622, 1 part of ultraviolet absorber UV-326, and 0.5 part of antioxidant 168.

[0041] The preparation method of this self-adhesive metal sheet protective film includes the following steps: First, weigh the raw materials of the substrate layer according to the proportion, mix them, melt and extrude at 170 °C, filter, and blow film to obtain the substrate layer. Corona treat the substrate layer under the conditions of a power of 8 kW and a treatment speed of 20 m / min. Subsequently, weigh the raw materials of the adhesive layer according to the formula ratio, put each component into a high-speed mixer and mix and stir evenly. Coating is carried out on the surface of the substrate layer by the gravure coating method, and dried for 5 minutes under the condition of 90 °C hot air to cure and form the adhesive layer, thus obtaining the self-adhesive metal sheet protective film.

[0042] Comparative Example 4 This comparative example provides a self-adhesive metal sheet protective film, including a substrate layer with a thickness of 0.07 mm and an adhesive layer with a thickness of 0.15 mm; The substrate layer is composed of the following raw materials in parts by weight: 70 parts of polypropylene, 13 parts of ethylene-octene copolymer, 5 parts of nano-silica, 0.4 part of silane coupling agent, 0.9 part of hindered amine light stabilizer, 0.6 part of ultraviolet absorber, and 0.4 part of antioxidant; The adhesive layer is composed of the following raw materials in parts by weight: 35 parts of ethylene-vinyl acetate copolymer, 27 parts of organosilicon-modified acrylic resin, 17 parts of maleic anhydride grafted polypropylene, 7 parts of polytetrafluoroethylene micropowder, 5 parts of carbon nanotubes, 3.5 parts of nano-zinc oxide, 0.9 part of silane coupling agent KH550, 1.8 parts of hindered amine light stabilizer HALS-622, 1 part of ultraviolet absorber UV-326, and 0.5 part of antioxidant 168.

[0043] Among them, the carbon nanotubes need to be pretreated. The steps include: placing the carbon nanotubes in an ethanol solution containing 1% surfactant CTAB by mass fraction, ultrasonic treatment for 1.5 hours to break agglomeration, centrifuging at 8000 rpm to remove undispersed particles, and collecting the upper homogeneous dispersion; then oxidizing with 25% nitric acid by mass concentration at 55 °C for 35 minutes, washing with deionized water until neutral, and vacuum drying to obtain the pretreated carbon nanotubes; The preparation method of this self-adhesive metal sheet protective film includes the following steps: First, weigh the raw materials of the substrate layer according to the ratio, mix them, melt and extrude at 170 °C, filter, and blow film to obtain the substrate layer. Corona treatment is carried out on the substrate layer under the conditions of a power of 8 kW and a treatment speed of 20 m / min. Then, weigh the raw materials of the adhesive layer according to the formula ratio, put each component into a high-speed mixer and mix and stir evenly. Adopt the gravure coating method to coat on the surface of the substrate layer, and dry and cure for 5 minutes under the condition of 90 °C hot air to form the adhesive layer, thus obtaining the self-adhesive metal sheet protective film.

[0044] Comparative Example 5 This comparative example provides a self-adhesive metal sheet protective film, including a substrate layer with a thickness of 0.07 mm and an adhesive layer with a thickness of 0.15 mm; The substrate layer is composed of the following raw materials in parts by weight: 70 parts of polypropylene, 13 parts of ethylene-octene copolymer, 5 parts of nano-silica, 0.4 part of silane coupling agent, 0.9 part of hindered amine light stabilizer, 0.6 part of ultraviolet absorber, and 0.4 part of antioxidant; The adhesive layer is composed of the following raw materials in parts by weight: 35 parts of ethylene-vinyl acetate copolymer, 27 parts of organosilicon-modified acrylic resin, 17 parts of maleic anhydride-grafted polypropylene, 7 parts of polytetrafluoroethylene micropowder, 3.5 parts of nano-zinc oxide, 0.9 part of silane coupling agent KH550, 1.8 parts of hindered amine light stabilizer HALS-622, 1 part of ultraviolet absorber UV-326, and 0.5 part of antioxidant 168.

[0045] The preparation method of this self-adhesive metal sheet protective film comprises the following steps: First, weigh the raw materials of the substrate layer according to the proportion, mix them, melt and extrude at 170 °C, filter, and blow film to obtain the substrate layer. Corona treat the substrate layer under the conditions of a power of 8 kW and a processing speed of 20 m / min. Subsequently, weigh the raw materials of the adhesive layer according to the formula ratio, put each component into a high-speed mixer and mix and stir evenly. Coating is carried out on the surface of the substrate layer by the gravure coating method, and drying is carried out under the condition of hot air at 90 °C for 5 minutes to cure and form the adhesive layer, thus obtaining the self-adhesive metal sheet protective film.

[0046] Comparative Example 6 This comparative example provides a self-adhesive metal sheet protective film, including a substrate layer with a thickness of 0.07 mm and an adhesive layer with a thickness of 0.15 mm; The substrate layer is composed of the following raw materials in parts by weight: 70 parts of polypropylene, 13 parts of ethylene-octene copolymer, 5 parts of nano-silica, 0.4 part of silane coupling agent, 0.9 part of hindered amine light stabilizer, 0.6 part of ultraviolet absorber, and 0.4 part of antioxidant; The adhesive layer is composed of the following raw materials in parts by weight: 35 parts of ethylene-vinyl acetate copolymer, 27 parts of organosilicon-modified acrylic resin, 17 parts of maleic anhydride-grafted polypropylene, 7 parts of polytetrafluoroethylene micropowder, 5 parts of carbon nanotube / SiO2 nanocomposite, 0.9 part of silane coupling agent KH550, 1.8 parts of hindered amine light stabilizer HALS-622, 1 part of ultraviolet absorber UV-326, and 0.5 part of antioxidant 168.

[0047] Among them, the preparation method of the carbon nanotube / SiO2 nanocomposite includes: Place the carbon nanotubes in an ethanol solution containing 1% surfactant CTAB by mass fraction, ultrasonically treat for 1.5 hours to break the agglomeration, centrifuge at 8000 rpm to remove the undispersed particles, and collect the upper layer of the uniformly dispersed liquid; Subsequently, oxidize with 25% nitric acid by mass concentration at 55 °C for 35 minutes, wash with deionized water until neutral, and vacuum dry to obtain the pretreated carbon nanotubes; Mix tetraethyl orthosilicate, ethanol and water in a molar ratio of 1:4:4, adjust the pH to 2.5 with hydrochloric acid, add polyvinyl alcohol, and then carry out magnetic stirring at 250 rpm for 2.5 hours to form a transparent sol; the mass of polyvinyl alcohol is 0.5% of the total mass of tetraethyl orthosilicate, ethanol and water. Mix the pretreated carbon nanotubes with the transparent sol prepared from tetraethyl orthosilicate, ethanol and water, ultrasonically disperse for 30 min, then stir at 55 °C and 150 rpm for 5.5 h, cool to room temperature and let stand for 11 h, then vacuum dry at 75 °C for 2.5 h to remove the residual solvent, and finally calcine the vacuum-dried material at 400 °C under nitrogen protection for 2.5 h, and naturally cool to obtain the carbon nanotube / SiO2 nanocomposite; the mass of the pretreated carbon nanotubes is 8% of the mass of the transparent sol.

[0048] The preparation method of this self-adhesive metal sheet protective film includes the following steps: First, weigh the raw materials of the substrate layer according to the ratio, mix them, melt and extrude at 170 °C, filter, and blow film to obtain the substrate layer. Carry out corona treatment on the substrate layer under the conditions of a power of 8 kW and a processing speed of 20 m / min. Then weigh the raw materials of the adhesive layer according to the formula ratio, put each component into a high-speed mixer and mix and stir evenly, coat on the surface of the substrate layer by the gravure coating method, and dry and cure at 90 °C hot air for 5 minutes to form the adhesive layer, thus obtaining the self-adhesive metal sheet protective film.

[0049] Test Example 1: The protective films prepared in the foregoing Examples 1-3 and Comparative Examples 1-6 were tested as follows: 1. Adhesion test: Test according to GB / T 9286-2021; 2. Residual glue test: Stick the protective film for metal surface on a stainless steel plate, press with a 25 kg heavy object for 7 days, tear off the protective film for metal surface, and observe the residual glue situation; 3. High temperature and high humidity resistance: Refer to GB / T 32368-2015 "Test Method for High Temperature and High Humidity Aging of Adhesive Tapes", stick the self-adhesive protective film on a stainless steel plate with a smooth surface, then place the stainless steel plate in an oven at 100 °C for baking. Take out one stainless steel plate every 24 h, wait for the stainless steel plate to cool naturally to room temperature, observe the deformation of the bonding part between the protective film and the stainless steel plate, and observe whether there is residual glue on the stainless steel plate after peeling the protective film from the stainless steel plate; 4. Aging resistance: Refer to ASTM D4329-13 and irradiate at 300 W ultraviolet light and 50 °C for 240 h, observe whether the protective film has cracking, loss of gloss, peeling, powdering and deformation, and whether there is residual glue retention and shadow on the protected surface when the protective film is torn off.

[0050] The test results are shown in Table 1 below: Table 1

[0051] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A self-adhesive metal sheet protective film, characterized in that: It comprises a substrate layer having a thickness of 0.06-0.08 mm and an adhesive layer having a thickness of 0.14-0.16 mm; The substrate layer is composed of the following raw materials in parts by weight: 60-80 parts of polypropylene, 12-14 parts of ethylene-octene copolymer, 4-6 parts of nano-silicon dioxide, 0.3-0.5 parts of silane coupling agent, 0.8-1 parts of hindered amine light stabilizer, 0.5-0.7 parts of ultraviolet absorber and 0.3-0.5 parts of antioxidant; The adhesive layer is composed of the following raw materials in parts by weight: 30-40 parts of ethylene-vinyl acetate copolymer, 25-30 parts of silicone-modified acrylic resin, 15-20 parts of maleic anhydride grafted polypropylene, 6-8 parts of polytetrafluoroethylene micropowder, 4-6 parts of carbon nanotube / SiO2 nanocomposite material, 3-4 parts of nano zinc oxide, 0.8-1 part of silane coupling agent, 1.6-2 parts of hindered amine light stabilizer, 0.8-1.2 parts of ultraviolet absorber and 0.4-0.6 parts of antioxidant.

2. A self-adhesive metal sheet protective film according to claim 1, characterized in that: The preparation method of the carbon nanotube / SiO2 nanocomposite material comprises: mixing the pretreated carbon nanotubes with a transparent sol prepared by tetraethyl orthosilicate, ethanol and water, stirring for 5-6 hours at 50-60°C and 100-200rpm after ultrasonic dispersion for 30 minutes, standing for 10-12 hours after cooling to room temperature, then vacuum drying for 2-3 hours at 70-80°C to remove residual solvent, and finally calcining the vacuum-dried material at 380-420°C under nitrogen protection for 2-3 hours, and naturally cooling to obtain the carbon nanotube / SiO2 nanocomposite material.

3. A self-adhesive metal sheet protective film according to claim 2, characterized in that: The pretreatment method comprises: placing the carbon nanotubes in an ethanol solution containing 1% by mass of a surfactant CTAB, performing ultrasonic treatment for 1-2 hours to break up the agglomeration, collecting the upper uniform dispersion after centrifugation; then oxidizing with 20%-30% by mass concentration of nitric acid at 50-60° C. for 30-40 minutes, washing with deionized water until neutral, and vacuum drying to obtain the pretreated carbon nanotubes.

4. A self-adhesive metal sheet protective film according to claim 2, characterized in that: The preparation method of the transparent sol comprises: mixing tetraethyl orthosilicate, ethanol and water in a molar ratio of 1:4:4, adjusting the pH to 2-3 with hydrochloric acid, adding polyvinyl alcohol, and stirring magnetically at a speed of 200-300 rpm for 2-3 hours to form a transparent sol.

5. A self-adhesive metal sheet protective film according to claim 4, characterized in that: The mass of the polyvinyl alcohol is 0.4%-0.6% of the total mass of tetraethyl orthosilicate, ethanol and water.

6. A self-adhesive metal sheet protective film according to claim 2, characterized in that: The mass of the pretreated carbon nanotubes is 6%-10% of the mass of the transparent sol.

7. A self-adhesive metal sheet protective film according to claim 6, characterized in that: The silane coupling agent is silane coupling agent KH550.

8. The self-adhesive metal sheet protective film according to claim 1, characterized in that: The hindered amine light stabilizer is hindered amine light stabilizer HALS-622, the ultraviolet absorber is UV-326 ultraviolet absorber, and the antioxidant is antioxidant 168.

9. A method for preparing a self-adhesive metal sheet protective film according to any one of claims 1 to 8, characterized in that: The steps include: Firstly, the raw materials of the substrate layer are weighed and mixed according to a proportion, melt-extruded at 160-180° C., filtered, and blown to obtain the substrate layer, and the substrate layer is subjected to corona treatment at a power of 6-10 kW and a processing speed of 15-25 m / min. Subsequently, the raw materials of the adhesive layer are weighed according to the formula proportion, and each component is put into a high-speed mixer for mixing and stirring evenly. The substrate layer is coated on the surface by a gravure coating method, and the adhesive layer is cured to obtain a self-adhesive metal sheet protective film.

10. The method for preparing the self-adhesive metal sheet protective film according to claim 9, characterized in that: The curing step includes: drying under hot air conditions of 80-100° C. for 4-6 minutes.

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